1. Field of the Invention
The present invention relates to a conveying apparatus which conveys a workpiece.
2. Description of the Related Art
In some cases, a workman works on a workpiece conveyed by a conveying apparatus not only on a surface of the workpiece he faces, but also on leading and trailing surfaces in the conveyance direction. In this case, the working efficiency improves if working spaces are provided in front of and behind the workpiece. This method is effective especially in an assembly process for a large-size product such as an automobile or engine, because the workman cannot reach the leading and trailing surfaces of a workpiece if a conveyor exists below the workpiece.
Hence, for example, the automobile assembly process often adopts a system of suspending a workpiece from above and conveying it. However, this system requires large-scale equipment to prevent rolling off a workpiece and so on. Further, the conveyor is arranged above a workpiece, and maintenance requires work at a high position.
A conceivable effective measure is a cantilever conveying apparatus which supports a workpiece in the horizontal direction (side surface of the workpiece) perpendicular to the conveyance direction. Examples of the cantilever conveying apparatus are disclosed in Japanese Patent Laid-Open No. 2005-178936 and International Publication No. 2009/128128.
A conveying apparatus disclosed in Japanese Patent Laid-Open No. 2005-178936 holds a workpiece by pinching both upper and lower guiderails by upper and lower rollers arranged on the side of a holding mount. A conveying apparatus disclosed in International Publication No. 2009/128128 holds a workpiece by pinching a guiderail from below and above by upper and lower rollers of a holding mount.
However, when a workpiece is large and heavy, each of the above-mentioned conveying apparatuses requires large-scale equipment to ensure strength. Particularly in the above-mentioned conveying apparatus, the distance between the guiderails needs to be increased vertically to widen the interval between support points. As described above, maintenance is accompanied by work at a high position.